AdBlue® is a urea solution in de-ionised water, and it reacts with a number of common metals. Those metals corrode, and the corrosion products dissolve into the AdBlue. That matters because ISO 22241-1 sets very tight limits on metals: copper, zinc, chromium and nickel at no more than 0.2 mg/kg, and aluminium, iron and several others at no more than 0.5 mg/kg. A single brass fitting in the wrong place can be enough to cause problems over time.
Getting materials right is one of the most cost-effective ways to protect your AdBlue and the SCR systems it goes into.
Compatible and incompatible materials
| Compatible | Not compatible |
|---|---|
| Stainless steel (304 and 316) | Carbon (mild) steel |
| HDPE (high-density polyethylene) | Aluminium |
| Polypropylene | Copper |
| PTFE | Brass |
| EPDM seals and hose | Zinc and galvanised steel |
| Fluoroelastomer seals |
Stainless steel grades 304 and 316 both suit AdBlue. Grade 316 is often chosen on coastal sites because it resists salt air better, but either works with the product itself.
The reason copper and brass are on the wrong side is partly chemistry you can smell. AdBlue slowly releases ammonia, and ammonia is well known for attacking copper and its alloys. Zinc coatings, aluminium and mild steel corrode in their own ways, and all of them shed metal into the liquid.
Equipment sold specifically for AdBlue is built from the compatible list. Problems usually come from general-purpose parts added on site.
Where the wrong materials sneak in
Most sites don't set out to use the wrong metal. It happens through small additions and substitutions:
- Brass fittings from the plumbing aisle. Tap adaptors, camlock fittings, ball valves and barbs are very often brass. They look like the right part and fit perfectly.
- Galvanised pipe and stands. A galvanised pipe run is fine for water, not for AdBlue. A galvanised stand is fine as long as the product never touches it.
- Aluminium funnels and jugs. Common in workshops and easy to grab.
- Pumps and nozzles from other liquids. Equipment built for diesel or oil often uses aluminium or cast iron components, and it carries residue as well.
- Mild steel drums and tanks. Second-hand steel containers corrode quickly and add iron to the product.
- Copper lines. Occasionally used in older workshop installations for other purposes and repurposed.
Seals, hoses and plastics
Metals get most of the attention, but the soft parts matter too. EPDM is the standard choice for AdBlue hose and seals, and fluoroelastomer seals are also compatible. PTFE is used for thread tape and some seals.
A few practical points:
- Use hose rated for AdBlue, not general water or diesel hose, whose linings and seals may not be suitable.
- Replace any seal of unknown material when you swap a fitting, rather than reusing whatever was there.
- HDPE and polypropylene containers are the norm, but they must be clean and dedicated. Plastic that has held other chemicals can absorb residues.
- Plastic parts exposed to sun age over time. Replace hoses and fittings that become cracked, chalky or brittle.
Materials also apply to anything that has held another product. Even a stainless steel tank or HDPE drum isn't suitable if it has held diesel, oil, coolant or mineral-containing water, because of the residue left behind.
A quick audit you can do today
Trace the path your AdBlue takes, from the container or tank outlet through every valve, fitting, hose, meter and filter to the nozzle. Look for yellow metal (brass or copper), dull grey metal that could be galvanised or aluminium, and any part you can't identify. Replace anything doubtful with a stainless steel or plastic equivalent designed for AdBlue. On most sites the audit takes less than half an hour and often turns up at least one fitting that shouldn't be there.
Keep a record of the parts you use for repairs, so the next person to fix a leak doesn't go back to the hardware store for a brass fitting.
How Liquidia can help
Liquidia supplies Piusi pumps, nozzles, meters, EPDM hose and fittings designed for AdBlue. See the accessories range, or ask us about a complete tank and dispensing setup built from compatible materials.